Trends in GeTe Thermoelectrics: From Fundamentals to Applications

Abstract

Germanium telluride (GeTe) with ultrafast ferroelectric transition, Rashba-like electronic transport, and anomalous phonon anharmonicity are historically studied for potential memorizing and thermoelectric applications. Due to recent breakthroughs in spintronics, valleytronics, orbitronics, pre-eminent GeTe thermoelectrics have re-attracted enormous interest from both academia and industries, with increasing reports of significant figure-of-merit over 2.7 and the maximum efficiency of up to 17.0%. Here, the emerging trends in advancing GeTe thermoelectrics, starting from fundamentals of phase transformation, crystal structure, bonding mechanisms, and transport characteristics, with a highlight on the roles of Ge_4s2 lone pairs, are timely overviewed. Technical insights in synthesis, characterization, property measurement, and computation are then summarized. After that, several innovative strategies for increasing the figure-of-merit, including entropy engineering, nanostructuring, and hybridization, which will further benefit near-room-temperature and n-type performance, are examined. Moreover, high-density and high-efficiency devices with broad working temperatures are discussed as a result of rational configurational and interfacial design. In the end, perspective remarks on the challenges and outlook envisaging for next-generation GeTe thermoelectrics, which will play a prominent role in future energy and environmental landscapes, are provided.